I became the youngest prince in the novel

Emperor Aurelian Agnes, founder of an empire and master of abyssal magic, one day falls asleep atop a book that portends his empire’s end. Waking up as a weak and sequestered prince in that future timeline, he must use his knowledge of the book and his unique magic to break the mold set before him and change the world’s impending end. Can he overcome an invading demon army, infighting royals, magical disasters, and even his own weak body, or will his empire fall for good?